Trying to understand the cumulative effect of breathing mods

[KingJoseph]

OK, so I understand that with an aftermarket exhaust on the Nismo, you sacrifice some of your low and mid range power for power in the higher rev band. Conversely, with the M370 intake manifold mod from Motordyne, it seems you gain in the low to mid range and lose a little top end.

Something tells me the two mods together don't necessarily offset the losses in a simple arithmetic type of way for an overall gain. Can anybody explain what to expect from the combination of two mods of this type either from a seat of the pants perspective or with dyno charts?

Further, I have high flow cats. At what point does this car have too LITTLE backpressure? If ever?

Thanks in advance.